From bc67b65de2ec972f80a365ba35982b54e17e38c3 Mon Sep 17 00:00:00 2001
From: Neil Webber <neil@webber.com>
Date: Thu, 7 Sep 2023 19:05:13 -0500
Subject: [PATCH] Add boot_file

---
 boot.py | 43 +++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 41 insertions(+), 2 deletions(-)

diff --git a/boot.py b/boot.py
index e615aa1..726da58 100644
--- a/boot.py
+++ b/boot.py
@@ -1,4 +1,7 @@
-def boot_hp(p, addr=0o10000):
+
+def boot_hp(p, /, *, addr=0o10000):
+    """Read the first 1KB of drive 0 into location 'addr'."""
+
     # this is the sort of thing that would be keyed in from
     # the console switches (if the machine was not equipped
     # with a boot rom option to hold it instead)
@@ -8,7 +11,7 @@ def boot_hp(p, addr=0o10000):
     # at zero is done elsewhere.
     #
     # NOTE WELL: THIS ASSUMES THE MACHINE IS IN RESET CONDITION WHICH
-    #            MEANS MANY OF THE DEVICE REGISTERS ARE KNOWN TO BE ZERO
+    #            MEANS MANY OF THE DEVICE REGISTERS ARE ASSUMED TO BE ZERO
     #
     #      MOV #176704,R0       -- note how used
     #      MOV #177000,-(R0)    -- word count - read 1K though boot really 512
@@ -29,6 +32,42 @@ def boot_hp(p, addr=0o10000):
     return addr
 
 
+def boot_file(p, fname, /, *, addr=0, little_endian=True, skipwords=8):
+    """Read a raw binary image of pdp11 data into location 'addr'."""
+
+    with open(fname, 'rb') as f:
+        bb = f.read()
+
+        # Two data format cases:
+        #   1) little_endian (the default)
+        #
+        #      The file is truly a binary image of pdp11 format data
+        #      and the words (pairs of bytes) in bb are in little endian
+        #      order. They will be assembled accordingly and the names
+        #      "low" and "hi" make sense.
+        #
+        #   2) not little_endian
+        #
+        #      Presumably the file has been byte-swapped already and
+        #      the words (pairs of bytes) in it are in big endian order.
+        #      They will be assembled accordingly, but the names "low"
+        #      and "hi" are backwards.
+        #
+
+        xi = iter(bb)
+        words = []
+        for low in xi:
+            hi = next(xi)
+            if little_endian:
+                words.append((hi << 8) | low)
+            else:
+                words.append((low << 8) | hi)    # see case 2) above
+
+        for a, w in enumerate(words[skipwords:]):
+            p.physmem[a] = w
+    return p
+
+
 if __name__ == "__main__":
     import time
     from machine import PDP1170